In addition to the ingredients indispensable for the washing process, such as surfactants and builder materials, laundry detergents usually also contain other ingredients, which can be summarized under the term washing auxiliaries and include such diverse groups of active ingredients such as foam regulators, graying inhibitors, soil-release active ingredients, bleaching agents, bleach activators and dye transfer inhibitors. Such auxiliaries also include substances of which the presence enhances the washing power of surfactants, without themselves generally having to exhibit pronounced surfactant behavior. Such substances are often referred to as washing power enhancers.
Soil-release active ingredients, as an auxiliary of a textile treatment agent, prevent dirt from accumulating directly on the surface of textiles and penetrating the textile material (for example the textile fiber), where it can be removed only with difficulty. Equipping the textile surface with what are known as soil-release active ingredients causes dirt to accumulate on the textile surface coated with soil-release active ingredient and thus come into direct contact only with this coating, but not with the textile fiber itself, and also prevents penetration into said textile fiber. The coating, inclusive of dirt, comes off as a result of a repeated washing process.
Document WO 98/58044 discloses laundry detergents that contain polyesters of terephthalic acid with alkylene oxides in combination with a specific anionic surfactant.
Polymers of ethylene terephthalate and polyethylene oxide terephthalate having a molecular weight of 5,000 to 200,000, and their use in liquid laundry detergents are described in German patent DE 28 57 293.
European patent EP 066 944 relates to textile treatment agents which contain a copolyester of ethylene glycol, polyethylene glycol, aromatic dicarboxylic acid and sulfonated aromatic dicarboxylic acid in specific molar ratios.
Document WO 2013/139726 relates to portions in the form of a single dose which comprise liquid laundry detergent provided with a water-soluble wrapping, said liquid laundry detergent containing a copolymer of ethylene terephthalate and polyethylene oxide terephthalate.
Even if the textile surface is not provided beforehand with an active soil-release active ingredient, it has been shown that some soil-release active ingredients can additionally cause an increase in the primary washing power of a laundry detergent on selected stains. It has been found that a soil-release active ingredient does not have this effect on the primary washing power across the entire spectrum of stains equally.
In particular, the removal of stains by one-time washing of soiled test materials under standard conditions is understood to mean the primary washing power. The secondary washing power relates, inter alia, to the extent of graying and encrustation on the textile fibers after repeated washing under standard conditions, for example after 20 or after 50 washes using the selected laundry detergent.